This invention relates in general to motor vehicle roll control systems.
Suspension systems for motor vehicles are known which isolate the vehicle load from irregularities in the terrain over which the vehicle travels. A semi-active suspension system, for example, normally includes a spring and a damper connected between the sprung and unsprung portions of the vehicle. Semi-active suspension systems are generally self-contained, and only react to the loads applied to them. In active suspension systems, by contrast, the reactions to the applied loads are positively supplied by electronically controlled hydraulic or pneumatic anti-roll lock mechanisms.
In addition to isolating the sprung portion of the vehicle from the road, it is desirable to stabilize the tendency of the sprung portion of the vehicle to tilt or roll relative to its unsprung portion when accelerating, decelerating or cornering at relatively high rates. Therefore, suspension systems have been proposed that attempt to maintain the vehicle in an essentially level position, regardless of the source of the force seeking to upset that position. For example, U.S. Pat. No. 4,206,935 to Sheppard et al., the disclosures of which are incorporated herein by reference, discloses a motor vehicle roll control system that includes anti-roll force adjustment means whereby the action of anti-roll bars can be modified within predetermined limits. Also, for example, U.S. Pat. No. 5,630,623 to Ganzel, the disclosures of which are incorporated herein by reference, discloses a semi-active system for controlling the roll of a motor vehicle including an anti-roll lock mechanism connected between an unsprung portion of the vehicle and a sprung portion of the vehicle, first and second pressure control valves, and first and second check valves.
Conventional anti-roll bars act to limit sway or roll of the vehicle to improve performance and improve comfort when cornering. Conventional anti-roll bars are permanently connected between sprung and unsprung parts of the vehicle and thus are always operational, which causes the vehicle to generally have a firmer ride than may be desirable for greatest comfort when traveling straight. Vehicles without anti-roll bars, conversely, may be comfortable when traveling relatively straight, but may be uncomfortable due to excessive roll during cornering.